Tobacco smoking and exposure to second-hand smoke have been implicated in human diseases. The tar components of smoke demonstrate the greatest toxicity. However cigarettes which heat,but do not burn,tobacco deliver lower levels of tar. This study will therefore investigate the impact of an alternative tobacco-heating cigarette. Several measures of bronchoalveolar function, inflammation, pulmonary and cardiovascular physiology and exposure to mutagen will be assessed before and after switch to the alternative cigarette and compared with non-smokers.